Bollettino valanghe

East Slopes North

Northwest Avalanche Center
Vedi sulla mappa

Pericolo valanghe

Sun
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
3 · Marcato
Open full map
Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Small wet avalanches could occur naturally at low elevations, and you can trigger avalanches at upper elevations where the wind drifts the new snow. Avalanches on deeper weak layers are difficult to predict, though there's still a chance for one in areas of shallower snowpack or due to a large trigger like a cornice fall. Steer clear of steep and unsupported slopes, and give yourself a wide buffer from complex terrain. 

Problemi valanghivi

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–1.5

    Expect small wet avalanches in the surface snow at low elevations. You may even see a number of natural avalanches in steep terrain. Stay off of and out from under steep, rocky slopes below about 4,000ft. Even if wet avalanches remain small, they could be forceful enough to push you into rocks or trees.

    Rain and wet snow will fall up to 4,000ft. While this won't be a deluge, it should be enough to initiate avalanches at low elevations. Expect even warmer temperatures on Sunday.

    (12/7/2023)

    Wet loose debris in the Liberty Bell slide paths on Hwy 20

    Photo: Willie Webster

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    Look for blowing snow, freshly deposited drifts, and cracks shooting from your feet or machine to indicate where you can trigger an avalanche. The general wind direction will be southwest. Windward, loaded slopes steeper than 35 degrees will be the most dangerous. Stick to lower-angle or wind-sheltered terrain. Use extra caution near cornices while traveling on ridges, and make sure to give them plenty of space. There have been multiple reports of recent cornice falls during the last warm-up, including some that triggered deep avalanches. Consider that triggering a smaller wind slab avalanche could be enough to gouge into deeper layers, resulting in a very dangerous slide.

    (1/26/2024)

    Wind-sculpted features at upper elevations in the Blue Lake basin.

    Photo: Will Govus

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–2.5

    While these avalanches are difficult for humans to trigger, they're not out of the question. They could be 2 to 3 feet deep and destructive. The coming warm-up could be enough to make avalanches easier to trigger or bring another round of cornice fall-initiated slides. Minimize your exposure to overhead cornices. Choose well-supported and lower-angle terrain. Stop and regroup in safer areas, with a wide buffer away from potential runout zones of overhead slopes.  Use extra caution east of Cutthroat Lake, where the snowpack is shallower.

    There are two problematic weak layers: small facets buried on or around January 8th in the top 1/2 of the snowpack and a series of crusts and large weak grains from December in the lower 1/3rd of the snowpack. These layers were reactivated by an intense storm on January 17th, resulting in natural avalanches. Since a warm-up on the 20th, we've received two reports of recent cornice-triggered avalanches on deeper layers and other cornice falls, resulting in only small avalanches. Observations of large rumbling collapses have slowed. We continue to get reports of snowpack tests indicating propagation.

    (1/25/2024)

    A recent natural avalanche (D1.5) likely ran on an older weak layer and may have been initiated by cornice fall. Poster/Pika Pk NE, 7,2000ft

    Photo: North Cascades Mountain Guides

Avalanche Discussion

On Friday, observers triggered a small wind slab avalanche in Liberty Bowl near Blue Lake. An NWAC forecaster near Varden Creek (NNE, 5,400ft) found propagating test results on the early January facets in the middle of a shallow snowpack (65cm with HS 117cm). On Thursday, a recent natural avalanche was reported from the Hairpin Valley on Poster/Pika Peak, NE, 7,200ft. Observers believe the avalanche may have been initiated by a cornice fall and ran on a weak layer in the top 1/3 of the snowpack (50cm below the surface with HS 150cm).

On the 24th, NWAC forecasters found 3 inches of new snow near Blue Lake. At a profile site (NW, 6,650ft), they found propagating test results on the January 8th facets ↓65cm and sudden collapse failures on old facets and crusts from December. The structure of older, stiff slabs over the thin, weak layer of January 8th facets, ~2 feet below the surface, matches a profile near the Poster Peak avalanche. On the 23rd, a forecaster reported a number of small, loose dry and wet avalanches in very steep, craggy terrain. Warming temperatures moistened snow surfaces up to about 6,000ft on all aspects. 

Other recent observations pertinent to persistent slabs are: 

  • Another large cornice-triggered avalanche in Cutthroat drainage ran on a deeper weak layer, likely occurring on the 21st. Deeper crowns were spotted since the January 16th storm, though visibility was poor.
  • On the 21st, an observer in the Twisp River area found that the mid-December crust produced unstable propagation saw test results. They also experienced loud whumphs that shook trees as the collapse propagated widely across the terrain.
  • Observers reported a couple of older D2.5 avalanches that ran on deeper weak layers near Hart's Pass, likely around the storm of Jan 17th. These occurred on an east aspect at 7,000ft and a west aspect at 5,800ft.

If you're in the mountains, please let us know what you find.

Regioni coperte